There are numerous instances where it is necessary to transmit a message of a localized nature to someone, and which needs to be updated on a regular but not instantaneous basis. Examples of such instances include promotions offered by a nearby store or mall, commentaries on pieces of art in a museum, or the nature, cost and location of sale items in a supermarket. Currently, information of a localized nature can be communicated in a number of ways. Foremost are signs with pictograms or reading material. However, signs require visual attention, which may distract the person the message is directed to. Signs may also be difficult to find in a visually cluttered environment. Another method is a sound broadcast. However, sound broadcasts by their nature are directed at everyone within a particular space. A sound broadcast also must be repeated over and over again, consequently requiring such broadcasts be kept relatively short. Sound broadcasts are typically used only for warnings or guided visits.
Another method is a device receiving the message in a wireless fashion, such as via infrared or radio frequency. The devices reconstruct the message in text or auditory format. This method requires an intelligent network of localized transmitters and can be costly to install and maintain. Infrared and radio frequency communications face other limitations as well. Infrared is strongly directional and positioning within the room is very important. Radio frequency (RF) is sensitive to interference from emitters in other locations or other RF devices. Compliance with the many RF regulations around the world creates additional costs for RF systems.Another method is a portable device carried by a user which stores a number of messages in memory. For example, systems based on messages prerecorded on a tape player have been in use in museums for some years. They are advantageous because they provide a personalized experience for the user and are relatively simple and inexpensive to install and maintain since no networks are involved. However, they face a number of drawbacks. The user must specify his location to receive the relevant message, and he must visit the exhibits in a predetermined sequence since the messages are not randomly accessible. The action required from the user reduces the effectiveness of this method. Also the messages can not be readily altered. This system could be improved if the message corresponding to the user's location were automatically determined. Various approaches have been proposed to achieve this objective, such as ultrasonic or radio transmitters which function as location beacons. However, they suffer from interference and cost problems.
Accordingly, there is a need for a position dependent information retrieval system that solves the shortcomings of the above described systems.